Playing music locally uploaded to Spotify through the sidebar player

As it stands this doesn't seem to be an option since the version of Spotify on the sidebar is Browser Spotify, but there should at least be a music player for local files. Maybe through a rudimentary player that you upload files to instead of making it read from your directory

In particular these are:

• adjusting the area of the New Tab button to include the very top of the screen, instead of having to "aim" slightly. Probably something long-time users adjust to but it would be nice
• merging tabs in separate windows seems to be impossible, or if it is possible it's not very intuitive. Specifically by dragging the tab in a minimized window into the tab bar at the top of a full screen window
• a lot of times, adding a new extension will not work until the browser is restarted